Hydraulic power servomotor control



June 15, 1954 D- w, |RW| 2,681,043

HYDRAULIC POWER sERvOMOToR CONTROL Filed Dec. so, 1949 4 Sheets-Sheet 1gg l ZM s @M RM Hls ATToRN'E.

June 15, 1954 D. w. IRWIN HYDRAULIC POWER sERvOMOTOR CONTROL 4Sh'eetS-Sheet 2 Filed Dec. 30, 1949 INVTORZ H ls ATTORNE June 15, 1954D. w. IRWIN HYDRAULIC POWER SERVOMOTOR CONTROL 4 Shets-Sheet I5 FiledDec. 30, 1949 June 15, 1954 D. w. IRWIN HYDRAULIC POWER SERVOMOTORCONTROL 4 Sheets-Sheet 4 Filed Dec. 30, 1949 |Nv NToR:

HIS ATTQRNEYS.

Patented June 15, 1954 UNITED STATE @ATENT OFFICE HYDRAULIC POWERSERVOMOTOR CONTROL Application December 30, 1949, Serial No. 135,875

Claims.

This invention relates to fluid pressure operated motors for adjustingcontrol surfaces on aircraft or for relatively moving one or more partsof a machine or other device in which a small amount of input force isused for controlling or regulating a large output force.

One of the objects of the invention is to provide a fluid pressure motorin which a reversing valve is disposed within the motor and iscompensated or balanced, thereby causing a smoother and more uniformoperation of the motor.

Another object of the invention is to provide a fluid pressure motorhaving a reversing valve that is vented to atmosphere through the pistonrod.

A further object of the invention is to provide a floating bushing in aiiuid pressure operated motor that will cause the motor to operate moresmoothly.

Still another obje-ct of the invention is to provide a reciprocatingfluid pressure operated motor in which the reversing valve is disposedwithin the piston and in which integral pressure operated valves areprovided in by-pass passageways for controlling and directing the flowof the operating iiuid from one end of the motor to the other in theevent of pressure fail#- ure and manual operation is desired.

The invention consists in the provision of a fluid pressure operatedmotor having a reverse ing valve means disposed within the cylinder ofthe motor, the p-iston having compensating means therein, one side ofwhich is vented to atmosphere through the piston rod in which thebalancing of discharge and applied pressure nuids occurs between thecompensating means and one of the reversing valve lands, or the valvecontrolrod on another reversing valve land, thereby causing the valveand the motor to operatesinoothly and uniformly.

This invention also consists in the provision of a oating bushing forthe piston rod of a fluid pressure operated motor.

In the drawings:

Fig, 1 is an end View of the motor, the rod fittings being omitted,

Fg. 2 is a sectional View taken substantially along the line 2-2 of 1,

Fig. 3 is a sectional view taken substantially along the line 3-3of Fig.l,

Fig. 4 is a view of the fluid pressure motor showing the return flowpassages adjusted for operating the motor in either direction and takenalong the line llof Fig. l,

Fig. 5 is a'sectional view taken substantially along the line 5 5 ofFig. 1 showing the reversing valve in neutral position,

Fig. 6 is a view similar to Fig. 5 showing the reversing valve moved tothe right,

Fig. 7 is a view similar to Fig. 5 showing the reversing valve moved tothe left; and

Fig. 8 is a sectional View taken substantially along `the line 8 8 ofFig. 1.

The invention is embodied in a device illustrated in the several viewsof the drawings in which the numeral I designates a cylinder casing fora duid pressure motor having cylinder heads 2 and 3 threaded onto eachend thereof, loclrnuts [i being provided for locking the heads on thecasing I. Each of the heads 2 and 3 is provided with passageways 5 and 6for connecting the chambers 'I and i3 with suitable devices for testpurposes. These passageways are ordinarily closed by plugs (not shown)after testing is completed.

A piston t is slidable within the bore or" cylinder I. This piston isprovided with a valve control rod I9 and a piston rod i I extendingthrough noa-ting bushings I2 and i3, respectively, and disposed in heads2 and 3. Pressure sealing rings Iii, I4 are disposed between rod It,bushing I2 and head 2, and pressure sealing rings I5 are similarlydisposed between rod II, bushing I 3 and head 3 for preventing leakageof fluid pressure from chambers l and 8. Pressure sealing rings i6prevent the escape of iluidy pressure from the chambers between heads 2and 3 and the cylinder casing I.

The valve control rod It extends into a bore in piston t and a sealingring Il is disposed therebetween. A valve IS is threaded into valvecontrol rod it and provided with valve lands i9 and 2t cooperating withvalve land apertures 2l and 22 out in piston 9, the relative position ofthe lands and passageways determining the direction of iiuid flowthrough the piston and, therefore, the direction of movement of piston 9relative to the cylinder casing I.

Thelpiston is provided with a plurality of passageways 23, 2t, 25 and 26bored in the piston, thus preventing distortion of the cylinder casingby reason of the high pressure acting thereon as would be'the case ir"the passageways were grooves out in the piston surface. Thesepassageways connect with radial passageways which selectively connect asource of fluid pres sure supply tochainbers 'i and 8, depending uponthe relative position of valve Iii with respect to valve land openings2l and 22. Fluid pres sure is introduced into the motor by means of 3 afitting 3|, the bore of which connects with a bore 32 in valve controlrod It, the tting being provided with pressure sealing rings 33 forpreventing the escape of pressure uid between the fitting and the valvecontrol rod. r"he bore 52 connects with the radial duct 3ft connectedwith the space between lands I9 and 2B, after which the pressure uid isselectively directed to chambers 'I and 8.

rhe .operating i'iuid is selectively exhausted from chambers 'l and 8through a fitting 35 mounted on piston rod Ii. The bore in iitting 35connects with a bore 36- in the piston rod. Sealing rings 3'! are dispodbetween the fitting 55 and piston rod II for preventing leakage ofpressure fluid. rI"he piston rod II is provided with a head 3S having aperipheral groove therein in which a sealing ring 59 is located thatcooperates with a bore in piston 9, The left hand end of the piston rodI I is threaded into the piston bore, said end of rod I I being boredand slidably receiving compensating piston d provided with a sealingring ill, the piston being secured to valve i8 for movement therewith. Achamber l2 is provided in piston 9 between land 26, compensating pistonse and the left hand end of head 38; and a chamber 23 is formed in thepiston between head 33 and the threaded end of piston rod II connectingwith the bore 35 in the piston rod.

The compensating piston l5 in the bore in the end of piston rod Il formsa chamber dit therein and entrapped air escapes to atmosphere through aconduit 45 threaded into head 35. rl'his conduit is also supported in acollar i6 formed in piston rod I I and leads to atmosphere through aduct il in eye bolt 8 threaded into piston rod Il. An eye bolt 4S isthreaded into the valve control rod IIB, it being connected to a controllever in the cock pit or to a machine operators control station. The eyebolt i3 is connected to a part to be moved relative to another. Inasmuchas the cylinder is rigidly mounted by trunnions t, the movable elementis the piston, although in some instances the cylinder may be moved withthe piston held stationary.

The piston S is provided with a pair of passageways el (Fig. 8)extending through the piston parallel with its longitudinal axis. Apressure responsive valve 52, slidable in a bore 55, is actuated bypressure uid and controls the closed position or the valves while aspring 53 returns them to open position in the event of pressurefailure. The pressure duid for operating valve 52 is derived from thatpresent in the space between valve lands I2 and 2li, there beingsuitable ducts 54 formed in piston for connecting the space with thebore in which the valve is slidably mounted. The direction of movementof piston 9 relative to the cylinder casing I is dependent upon theposition of valve lands i5 and 25 relative to valve land openings 2| and22.

Communication between certain chambers in one end of the piston and thechambers in the other end or the piston is established through passagesformed therein. Chamber 58 is in communication with chamber l2 throughduct 56 and radial passages cut in the piston. An additional radialpassageway is formed in the piston that establishes communicationbetween chamber 53 and chamber 53. This structure is clearly illustratedin Figure e.

It is assumed that the device is in the position illustrated in Fig. 5which shows the neutral position of the reversing valve wherein means I8and 34 are connected to means 2i and 22, while 4 means I9 and 20 shut oichambers 58 and d2 from passages 23 to 28, and that the relative motionbetween piston 91 and the cylinder casing I is to be toward the left.The valve I8 will, therefore, be moved to the left such that valve landopening 2| will be in communication with the pressure fluid in the spacebetween lands IS and 25. The pressure uid will now flow from bore 32 inthe piston rod I I into valve I8, through radial ducts 34, the spacebetween lands I9 and 20, through valve land opening 2l into radialpassageways 2l and 28 (Figs, 2 and 7) and passageways 23 and 24, thenceinto chamber 8. The admission of pressure Iluid into the chamber Il willcontinue to move piston 9 toward the left as long as land 29 is notpositioned over opening 22. When valve land 2li covers opening 22 afterthe valve rod i9 is no longer manually actuated, the motion of piston Elwill stop since the return low passages for the fluid in chamber I areclosed. The duid in chamber l is forced therefrom, by the motion ofpiston 9, through passageways 25 and 26 (Figs. 3, l and 7); throughradial ducts 29 and 3B; into the space about the right hand end of valveI8; and thence into chamber d2. This fluid also acts on the end of thecompensating piston 4Q. The return fluid then enters ducts 56 that arein communication with chamber 53, passing through ducts 51 in thethreaded end of the piston rod II, into bore 35 and out through fitting35. The extent and rate of movement is determined by the rate and amountof iluid forced out of chamber T. Air for breathing is supplied tochamber "It through conduit I5 and duct dl because the compensatingpiston @il is moved to the left in the bore.

Reverse or right hand relative movement of piston B and the cylindercasing I is initiated by moving the valve control rod lil and attachedvalve It to the right, as shown in Fig. 6. This movement will connectthe pressure fluid between valve lands IS and 29 with valve landaperture 22 and with radial passageways 29 and 30 (Figs. 3 and 6), afterwhich it will be conducted through passageways 25 and 2t into chamber l.This will cause piston 9 to move to the right, thus shutting off thereturn ow and stopping movement of the piston after a given movementthereof. Fluid is exhausted from chamber 8, by the motion of piston 9,through passageways 23 and 2d (Fig. 2) and passes through aperture 2|into chamber 5S, ducts 55 in the piston of chamber d3, ducts 5l, bore 36and fitting 35. Since the movement of valve IB was to the right, air inchamber l will be exhausted to atmosphere through conduit l5 and ductlll. The rate and extent of movement of the piston is controlled in thesame manner as for the left hand movement. The piston 9 may be movedmanually in cylinder l when the pressure rluid operated valve 52 hasbeen opened upon release of iiuid in the space between valve lands I9and 25, spring 53 forcing it to open position. When these valves areopen, iluid will iiow freely through passageways 5I between chambers Iand Il. As long as there is pressure fluid present in the system, valveI8 will hold and lock iiuid in the end of the cylinder casing to whichit has been directed.

The floating bushings l2 and I3 cause the fluid motor to operate moreuniformly, thus eliminating the erratic motions characterizing priorconstruction.

The piston 9 is locked in position by having the entering pressure fluidapplied to both ends thereof when the valve I8 is in neutral position,

as shown in Fig. 5. The lands i9 and 20 are slightly smaller in lengththan the diameter of the apertures 2i and 22, thus permitting the fluidin the space between the lands to pass through the apertures. Thelocking is accomplished by moving the piston relative to the valve a fewthousandths of an inch for relieving the pressure in one end of thecylinder and holding it in the other end thereof. After passing throughaperture 2i, pressure fluid enters passageways 225, 2 and 26, 3B, andthen to chamber l, thus acting on the left hand end of piston S. Afterpassing through aperture 22, the pressure uid enters passagevvays 23, 21and 2li, 28 and then to chamber 8, thus acting on the right hand end ofpiston 9 and locking the piston in neutral position. It should beunderstood that the piston d is only effectively locked against externalforces when they are less than the pressure of the source of pressureiluid supply. When the external forces are greater, then they will causemovement of the control cylinder.

Movement of the Piston 9 relative to cylinder casing i is controlled byregulating the rate at which the luidin either of chambers 'l or 8 flowstherefrom through return chamber 58, ducts 5E, chambers i2 and 133,ducts 51, thence through passageway $6 and iitting 35. Regardless of thedirection or movement of piston Si, the rate and extent ci 'movement isdependent upon the amount and rate of iiuid drawn from either ofchambers l or 8, depending upon the adjusted position of valve i8. Whenthe valve I8 is in neutral position, pressure balancing thereon is ob-Viated by reason of the fact that lands I9 and '2c are so located on thevalve that flow of pressure fluid into chambers 58 and 'i2 is prevented.The valve i3 is substantially balanced in its adjustment when set forright hand relative movement of piston Q and the cylinder casing l. Theen ering pressure nuid acts on lands I9 or 2t and the return pressureiluid acts on the end of rod itl. The area of the rod il! and theeffective area of lands l?. or 2G are so proportioned that there is atendency for return of valve i8 to its normal position by reason of thereturn pressure iluid acting on rod Iii. The valve I8 is alsosubstantiallg.,7 balanced in its adjustment when set for left handmovement of piston 9 and the cylinder casing i. The entering pressurefluid acts on lands i9 and 2E and the return pressure iluid acts on thecompensating piston 4 Whose elicotive area is equal to the eiective areaof rod iii. The effective areas of lands i9 and 2i) and the piston d@are so proportioned that there is a tendency for return of valve iS toits neutral position by reason of the return pressure duid acting oncompensating piston im. The manual force moving the valve I8 is opposedby the force created by the return pressure fluid acting on piston tilor rod lo in either direction of relative motion of piston 9 andcylinder i, thus tending to move valve I8 to its neutral position.

Reverse movement or piston rod il by an external force acting thereon isresisted by the necessity of moving piston 8 relative to valve i8. Thistends to drop the pressure on the return side or" the circuit, thusholding the incoming nuid on the input side of the circuit. rhe piston geffectively prevents the external force moving it unless said force isof such magnitude as to overcome the force applied to the piston by theincoming pressure iiuid. The force tending to restore the valve toneutral position is produced in the following manner: the effective areaof the passageway through chambers 58 and 42 has a smallercross-sectional area than the eiective area of ducts 5G, 5l and chamberi3. Therefore when the valve it is moved to the right, the return flowthrough passageway 24, aperture 2i, to chamber 5B creates a backpressure in chamber a8 by reason of the restricting effect of thepassage of duid through chamber 58 to the duct thus working on or beingapplied to the larger effective area or the control rod l il extendinginto the chamber 5S over the effective area of the valve land le,thereby producing a force tending to return the valve to neutralposition. Because ci this restricting effect the back pressure built upin chamber 5S is high-er than the pressure built up in chamber d2 eventhough they are interconnected. Ducts 55 and '5T having a largerefier-.tive area than the passage from chamber 53 'to duct 5t allows afree flow of fluid to the bore S5.

Movement of the valve I8 to the left creates the saine restoring forcein the chamber d2 in the same manner as described for the severalpassagcways and ducts as described above in connection with chamber 53.Thus during movement or under dynamic conditions of flow, there isalways a force tending to restore the valve Iii to neutral.

What I claim is:

l. A iiuid pressure loperated device comprising a cylinder, a piston insaid cylinder for forming two chambers therein, a valve control rodextending through one end of said cylinder and having a bore thereinfor'conducting pressure fluid into said piston, the end of said rodextending into said piston responsive to exhaust fluid pressure, apiston rod connected to said piston and extending through the other endof said cylinder', said piston rod having a bore therein for conductingexhaust pressure fluid away from said piston, a reversing valveconnected tok said valve control rod for directing the flow of pressurefluid to and from said chambers and movable in said piston by a manualforce; and means on said valve having an area substantially equal to theeiiective area of said valve control rod acted upon by exhaust pressurefluid and located in said piston for substantially balancing the forceycreated by the exhaust pressure fluid against said manual force.

2. A fluid pressure operated device comprising a cylinder, a piston insaid cylinder for forming two chambers therein, a valve control rodextending through one end of said cylinder and having a bore therein forconducting pressure iiuid into said piston, a piston rod connected tosaid piston and extending through the other end of said cylinder, saidpiston rod having a bore therein for' conducting exhaust pressure fluidaway from said piston, a reversing valve connected to said valve controlrod for directing the ilow of pressure ii'uid to and from said chambersand when in neutral position directing the uid into both ci saidchambers and movable in said piston by a manual force; and means on saidvalve and in said piston for causing the force created by the exhaustpressure fluid to be placed in opposition to the manual force applied tosaid valve in a manner so that the valve will have a tendency to bemoved to neutral position when the intake fluid is selectivelyv directedinto either of said chambers.

3. A fluid pressure operated device comprising a cylinder, a piston insaid cylinderand having a bore therein, a head for each end of saidcylinder, a Valve control vrodand a piston rod connected to opposite'ends vof'said piston and extending control rod, and movable in saidpiston bore and acted on by exhaust pressure fluid, means for ventingair into and from said bore as said valve mounted piston is movedtherein; and means for placing the force created by the exhaust pressurefluid in opposition to the manually applied force and being proportionedfor moving the valve to neutral position when directing the intakepressure fluid to either end of said cylinder.

4. A fluid pressure operated device comprising a cylinder, a piston insaid cylinder provided with pressure fluid passageways, a valve bore anda cylinder bore therein, a head for each end of said cylinder, afloating bushing in each head, a rod extending through each bushing onerod being connected to said piston, a reversing valve in said valve boreand connected to the other of said rods and cooperating with thepassageways formed in said piston for selectively directing fluid toeither end of said cylinder and for directing exhaust fluid therefrom,the rod secured to said valve having an area on which exhaust pressurefluid is effective, said valve movable by a manual force applied to oneof said rods, a piston Secured to said reversing valve movable in saidpiston bore and having an area being acted on by exhaust pressure fluid,means for causing the force created by exhaust pressure fluid acting onsaid valve piston to be placed in opposition to said manual force; andmeans for venting the air in said piston cylinder bore to atmosphere.

5. A iluid pressure operated device comprising a cylinder, a piston insaid cylinder having pressure iluid conducting passageways and acylinder bore therein, a head for each end of said cylinder,

a floating bushing in each head, a reversing valve in said piston, atube extending through one of said bushings and connected to said pistonfor conducting fluid away from the piston, a tube connected to saidreversing valve and movable by a manually applied force and extendingthrough the other of said bushings for conducting uid toward saidpiston, said tube having an area acted on by exhaust pressure fluid,said tube -when moved adjusting said valve for cooperation with saidpassageways for selectively directing iuid to either end of saidcylinder and for directing exhaust fluid therefrom, a piston associatedwith said reversing valve and movable in said cylinder bore and havingan area acted on by exhaust pressure fluid; and means for causing theforce created by the exhaust fluid selectively acting on said piston andon the tube for stopping fluid flow into said piston and to be placed inopposition to the manually applied force.

6. A fluid pressure operated device comprising a cylinder, a piston insaid cylinder having pressure iluid passageways and a cylinder boretherein, a head for each end of said cylinder, a hollow piston rodextending through each bushing, each rod connected to said piston, meansfor admitting pressure fluid into said cylinder through one of saidrods, a reversing valve connected to one of said rods and cooperatingwith the passageways in said piston for selectively directing uid toeither end of said cylinder and for directing exhaust fluid therefromthrough the other rod, the rod connected t0 said valve having an area tobe acted on by exhaust pressure fluid, said valve being movable by aforce manually applied to said last mentioned rod, a piston associatedwith said reversing valve and movable in said bore; and means on saidvalve for enabling pressure fluid entering said piston to be balancedand the exhaust fluid that selectively acts on said piston or on thehollo-W rod through which pressure fluid enters said means creating aforce so proportioned that the exhaust fluid tends to move saidreversing valve to neutral position in opposition to said manuallyapplied force after said rod is adjusted for selectively directingpressure fluid to either end of said cylinder.

7. A fluid pressure operated device comprising a cylinder, a pistonslidably mounted in said cylinder and forming a chamber in each end ofsaid cylinder, said piston having a bore therein and fluid conductingpassageways and ducts extending through said piston in an axialdirection, means for introducing pressure uid into said piston, areversing valve in said bore cooperating with said passageways forselectively directing pressure fluid into said chambers, a by-pass valvein each of said ducts, means for establishing communication between saidvalves and said bore for enabling pressure iiuid to close said valves;and means for opening said by-pass valves upon failure of the fluidsupply for permitting pressure fluid to freely move in said ductsthereby enabling said piston to be moved manually in said cylinder.

8. A fluid pressure operated device comprising a cylinder, a piston insaid cylinder providing a chamber in each end thereof and having a pairof ducts therein extending axially therethrough, means for introducingpressure fluid derived from a source external to the device into saidpiston, means for selectively releasing pressure fluid from either ofsaid chambers While the incoming pressure fluid acts in the otherchamber, a valve for each duct, means for causing pressure fluidintroduced into the piston to act on said valves for closing said ducts;and spring means for opening said valves upon failure of said pressurefor enabling the uid in said chambers to pass freely from one to theother when said piston is moved manually.

9. A fluid pressure operated device comprising a cylinder, a piston insaid cylinder having pressure fluid conducting passagevvays therein, ahead for each end of said cylinder, a reversing valve in said piston, atube extending through one of said heads and connected to said pistonfor conducting fluid away from the piston, a tube connected to saidreversing valve and movable by a manually applied force and extendingthrough the other of said heads for conducting fluid toward said piston,said tube when moved adjusting said valve for cooperation with saidpassageways for selectively directing fluid to either end of saidcylinder and for directing exhaust fluid therefrom; and means forcausing the force created by the exhaust fluid to be placed inopposition to the manually applied force.

l0. A fluid pressure operated device comprising a cylinder, a piston insaid cylinder having a bore therein, a head for each end of saidcylinder, a valve control rod and a piston rod connected to oppositeends of said piston extending through the head on each end of saidcylinder, the control rod having an area on which exhaust pressure uidis effective, a reversing valve connected to said control rod forselectively directing fluid to either side of said piston and fordirecting exhaust uid from said cylinder and movable by a manuallyapplied force; and a compensating piston connected to said valve andmovable in the bore in said piston, said compensating piston in saidbore having an effective area substantially equal to that of saidcontrol rod on which the exhaust pressure uid is effective, means forventing air into and out of said bore as said compensating piston ismoved therein, said compensating piston substantially balancing theforces created by said exhaust fluid acting on said compensating pistonWithin said bore and in the control rod against said manually appliedforce.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date Anderson May 24, 1910 Kiesel Mar. 27, 1923 Bragg Nov. 3, 1931Williams June 21, 1932 Christensen Oct. 25, 1938 Sorensen May 30, 1944Pohl Sept. 18, 1945 Boynton Jan. 29, 1946 Greenough July 22, 1947 ThomasJune 7, 1949 Tait Oct. 24, 1950 Kupiec Aug. 5, 1952

